1. Field of the Invention
The present invention relates to a tool replacing device for replacing tools in a tool storage magazine of a machining center when the workpiece on the machine is changed.
2. Description of the Prior Art
Nowadays, machining centers of a large variety of size and capacity are available. Even a small-sized machining center may employ a large number of tools, e.g. more than several tens of tools, to be stored in the tool storage magazine, if the work to be performed requires a large number of kinds or steps of machining. On the other hand, large-size machining centers for handling large-size workpieces require tools the sizes and, hence, the weights of which are correspondingly large. Usually, the group of tools in the tool storage magazine includes tools which are used specifically for the workpiece on the machine and tools which can be used commonly for other types of workpiece. Therefore, when the workpiece on the machine is changed, it is necessary to replace these specific tools by new tools which are required for the machining of the new workpiece. The replacement is necessary also with the common tools, when they are worn too much or broken and when they need inspection or check. The replacing work does not burden the operator so much when the tool storage magazine is a small-sized drum type one capable of holding several tools at most. However, when the number of the tools is large or when the tools are heavy, the replacing work heavily burdens the operator and the operator often faces a danger. This is quite inconvenient from the view point of safety management. To obviate this problem, it has been proposed to replace the tools automatically by preparing a spare or auxiliary magazine with the assist by a robot. This proposal, however, is not preferred because of the necessity of a specific robot which is generally expensive.